Rim structure particularly for cycle wheel with variable magnetic field electric generator

ABSTRACT

A rim structure, in particular for bicycles equipped with a current generator of the variable magnetic field type, comprises a circumferentially extending tubular body ( 2 ) from which a pair of opposite flanges ( 3 ) defining a seat ( 4 ) for housing a tyre (P) extends outwards. According to the invention the tubular body ( 2 ) comprises at least one annular peripheral side pocket ( 5 ) able to house a plurality of permanent magnets ( 6 ) aligned along one circumference. Spacer means ( 7 ) are also envisaged, said means being inserted in the side pocket ( 5 ) in order to keep the permanent magnets ( 6 ) at predetermined distances from each other.

TECHNICAL FIELD

The present invention is generally applicable in the field of wheeledvehicles and, in particular, relates to a rim structure, in particularfor bicycles equipped with a current generator, as well as to a methodand a machine for manufacturing this structure.

BACKGROUND ART

As is known, in bicycles where an available supply of electricity isrequired in order to power applications such as the front light and rearlight, generators—commonly referred to as “dynamos”—are used, saidgenerators being essentially alternators which receive the drivingmovement from a knurled roller which is arranged so as make contact, viaspring means, with one of the tyres of the bicycle.

In addition to the problems associated with deterioration of the movingparts which reduce the efficiency of the dynamo and cause a bothersomenoise, the dynamo has the major disadvantage that the voltage which isgenerated is dependent upon the speed of movement of the bicycle.

In order to overcome the main problems associated with the dynamo,current generator devices which use variable magnetic fields have beendeveloped.

These devices comprise a plurality of curved segments to be fixed to thespokes of the bicycle wheel, which support, in succession, a pluralityof permanent magnets.

The fork of the bicycle has fixed thereto, on a corresponding support, aplurality of pole shoes with associated windings around which an inducedcurrent flows, said current being due to the passing movement of themagnets which, being spaced from each other, generate an alternatingelectrical field.

The pole shoes are then connected to electrical accumulators which allowenergy to be supplied to the applications even when the bicycle is at astandstill.

This solution, however, also has problems associated in particular withthe fact that there is a discontinuity in the succession of permanentmagnets, since the curved segments are themselves arrangedcircumferentially spaced on the spokes.

The magnets are moreover not protected since they are arranged on curvedsegments which, being independent components on the outside of thebicycle wheel, may be moved, damaged and lost, being separated from thewheel itself.

WO00/59769 which is considered the nearest prior art to the invention,discloses a rim structure having all the features mentioned in thepreamble of the appended claim 1, and having permanent magnets which areinserted in a side pocket of the rim of the bicycle wheel.

However, the insertion of the permanent magnets into said side pocket atregular distance with respect to each other is rather difficult andunreliable, and does not prevent undesirable movements or vibrations ofthe magnets.

WO02/00492 also discloses a rim structure equipped with a currentgenerator of the variable magnetic field type. The current generatorcomprises plastic magnet holders with circular seats for housing aplurality of permanent magnets.

DISCLOSURE OF THE INVENTION

A main object of the present invention is that of overcoming theabovementioned drawbacks by providing a rim structure which eliminatesor substantially reduces the known problems associated with the supplyof electricity to bicycles using current generators of the variablemagnetic field type.

A particular object is that of providing a structure which, whencombined with a suitable current generator, operates in a uniform andsilent manner.

An additional object is that of providing a structure which allows alarge number of permanent magnets to be used.

A further object of the invention is that of providing a structure whichis able to protect the permanent magnets from dirt or accidental damage,preventing any dislodging or loss of efficiency of the said magnetsduring use.

Another particular object is that of providing a structure which issimple and economically advantageous in that it can be manufactured at alow cost using technology of the known type.

These objects, together with others which will appear more clearlybelow, are achieved by a rim structure in accordance with claim 1.

In a further aspect, the invention provides a method for manufacturingthe above rim structure in accordance with claim 10.

Yet in a further aspects, the invention provides a machine for carryingout the above methond in accordance with claim 15.

Owing to this particular rim structure and manufacturing method it willbe possible to use a large number of permanent magnets and to arrangethem in a safe and reliable manner, avoiding undesirable movement orvibration thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will be more clearlyunderstood in the light of the detailed description of some preferred,but not exclusive embodiments of a rim structure, a method for themanufacture thereof and a machine for implementing the method accordingto the invention, which are illustrated by way of a non-limiting examplewith the aid of the accompanying drawing sheets in which:

FIG. 1 shows a side view of a bicycle equipped with a rim having thestructure according to the invention;

FIG. 2 shows a side view of a wheel portion comprising a rim with thestructure according to the invention;

FIGS. 3 and 4 show two perspective views of respective enlarged detailsof a first example of embodiment of a structure according to theinvention;

FIG. 5 and FIG. 6 show two perspective views of enlarged details offurther examples of embodiment of a structure according to theinvention;

FIG. 7 and FIG. 8 show two front views of a rim structure according tothe invention, in two different configurations;

FIG. 9 shows a perspective view of a detail of the structures accordingto FIG. 5 and FIG. 6;

FIG. 10 shows a top plan view of a machine according to the invention;

FIG. 11 shows a side view of the machine according to FIG. 10;

FIG. 12 shows a block diagram of the manufacturing method according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

With particular reference to the above mentioned figures, a rimstructure is shown according to the invention, denoted in its entiretyby the reference number 1.

The rim structure 1 is mounted on a bicycle C equipped with a currentgenerator of the variable magnetic field type, known per se.

The rim 1 comprises a peripherally or circumferentially extendingtubular body—denoted in its entirety by the reference number 2—fromwhich a pair of opposite flanges 3 defining a seat 4 for housing a tyreP extends outwards.

According to the invention, the tubular body 2 comprises at least oneannular peripheral side pocket 5 which is able to house a plurality ofpermanent magnets 6 aligned along a circumference. Moreover, spacermeans, denoted overall by the reference number 7, are envisaged, saidspacer means being inserted inside the side pocket 5 so as to keep thepermanent magnets 6 suitably directed and situated at predetermineddistances from each other.

When the rim 1 is rotated, the permanent magnets 6 generate a variableelectric field on the windings of corresponding pole shoes—not shown inthe drawings and of a type known per se—facing the permanent magnets 6and arranged on a corresponding support S fixed to the frame of thebicycle C so as to follow the curved profile of the side pocket 5.

The windings of the pole shoes, although not shown in the drawings, areconnected to a voltage rectifier and stabilizer unit which is in turnconnected to an electric energy accumulator, which are both of a typeknown per se.

Preferably the distances between the permanent magnets 6 aresubstantially the same along the entire extension of the tubular body 2.Moreover, the side pocket 5 may have a quadrilateral, for exampleapproximately trapezoidal, cross-section, with an external annular wall8 which is substantially flat and perpendicular to the axis of rotationof the rim 1.

The tubular body 2 may have a pair of longitudinal ends 9, 10 facingeach other and connected by means of a pin 11. The tubular body 2 maycomprise a main cavity 12 which extends circumferentially and insidewhich the pin 11 may be inserted at the facing ends 9, 10. As analternative or in addition to the main cavity 12, the tubular body 2 maycomprise a secondary cavity 12′ inside which it is possible to insert asecond suitably shaped pin 11′. The secondary cavity 12′ may bepositioned opposite the side pocket 5. The pin 11 inserted into the maincavity 12 and the pin 11′ inserted into the secondary cavity 12′ have anexternal surface with a shape matching the internal surface of thecorresponding main cavity 12 and secondary cavity 12′ and havedimensions such that they may be inserted inside the latter by means ofinterference.

The tubular body 2 may be made of metallic material, such as for examplealuminium alloy, or synthetic material, such as for example PVC oranother polymer, or also a composite material, such as a reinforcedpolymer or carbon fibres.

The permanent magnets 6 may be preferably made of an alloy composed ofneodymium-iron-chromium in different percentages depending on thedesired electrical power. The permanent magnets 6 may also be treatedwith zinc or nickel.

In a first preferred example of embodiment, the spacer means 7 maycomprise an annular strip 13 of deformable laminar material insertedinside the side pocket 5. The permanent magnets 6 may be fixed to thestrip 13 inside suitable shaped seats 14 able to receive them.

Suitably the shaped seats 14 may be formed by transverse folds 15 ableto provide an undulating profile.

In greater detail, the base material of the strip 13 may be chosen fromamong non-magnetic or ferromagnetic materials. Yet, the base materialmay be chosen from among synthetic or composite materials which aresuitably reinforced.

In a further preferred example of embodiment, the spacer means 7 mayconsist of a plurality of non-magnetic inserts 16 which are for examplemade of synthetic material and arranged inside the side pocket 5alternating with the permanent magnets 6.

The rim structure 1 described above may be advantageously manufacturedby means of a method comprising the following steps.

During a first step a), a linear tubular body 2 having a lengthsubstantially equal to the circumferential extension of the rimstructure is prepared.

During the following steps b) and c), a plurality of permanent magnets 6as well as suitable means 7 for spacing said magnets are prepared.

During a fourth step d) the plurality of permanent magnets 6 and thespacer means 7 are inserted inside the side pocket 5 of the tubular body2 so as to keep the permanent magnets 6 at predetermined distances fromeach other.

During a fifth step e) the tubular body 2 is bent so as to provide thelatter with a circular shape with the longitudinal ends 9, 10substantially aligned.

During a final step f) the longitudinal ends 9, 10 are joined togetherso as to provide a continuous rim structure 1.

The step e) may be performed before or after the step d) for insertionof the permanent magnets 6 and the spacer means 7.

In a first example of embodiment the spacer means 7 may consist of astrip 13 of laminar material. The latter may be made by means of plasticdeformation, for example by means of moulding, so as to provide aplurality of shaped seats 14 with folded edges 15 at predetermineddistances from each other for receiving the permanent magnets 6.

Once the shaped seats 14 have been formed, the permanent magnets 6 maybe fixed there by means of an interference fit. Then the strip 13,together with the permanent magnets 6, may be inserted inside the sidepocket 5 substantially along the entire longitudinal extension of thetubular body 2 and may be cut at the longitudinal ends 9, 10 of thelatter.

In a second example of embodiment, the spacer means 7 may consist ofnon-magnetic inserts 16. In this case, the permanent magnets 6 may beinserted inside the side pocket 5 alternating with the non-magneticinserts 16.

Advantageously, the insertion step d) may be performed after the step e)for bending the tubular body 2. In particular the longitudinal ends 9,10 may be moved away from each other transversely, by elasticallydeforming the tubular body 2 as shown in FIG. 7, so as to allow accessto the side pocket 5 and the alternating insertion of the permanentmagnets 6 and the non-magnetic inserts 16 until the said pocket iscompletely filled.

The method described, with respect to solely the first example ofembodiment of the rim structure 1, is implemented by means of a machinewhich is denoted overall by 17.

The machine 17 may comprise means 18 for continuous feeding a strip 13of laminar material, means 19 for fixing a plurality of permanentmagnets 6 onto the strip 13, and means 20 for inserting the strip 13,together with the permanent magnets 6, inside the linear tubular body 2of predetermined length.

The machine 17 may also comprise, even though not shown in the drawings,means for cutting the strip 13 at the longitudinal ends 9, 10 of thetubular body 2, means for bending the tubular body 2, and means forjoining together the longitudinal ends 9 of the tubular body so as toprovide a unitary rim structure 1.

In particular, the fixing means 19 may comprise means for deforming thestrip 13, so as to provide a plurality of shaped seats 14 atpredetermined distances from each other, and a dispenser 21 for loadingpermanent magnets 6 into each shaped seat 14.

Suitably, the machine 17 may comprise a pair of racks 22 for collectingthe tubular bodies 2, before the latter are bent, and a control console23 for an operator.

From that described above, it is obvious that the rim structureaccording to the invention achieves the predefined objects and inparticular allows the provision of a large number of permanent magnetsand a drastic reduction in the risk of damage to or deterioration in theproperties of the said magnets.

The rim structure, the manufacturing method and the machine according tothe invention as defined in the accompanying claims may be subject tonumerous modifications and variations all falling within the inventiveidea expressed in the accompanying claims. All the details may bereplaced by other technically equivalent elements and the materials maydiffer according to the requirements, without departing from the scopeof the invention.

Although the rim structure, the manufacturing method and the machinehave been described with particular reference to the accompanyingfigures, the reference numbers used in the description and the claimsare used in order to facilitate understanding of the invention and donot limit in any way the scope of protection claimed.

1. A rim structure for bicycles equipped with a current generator of the variable magnetic field type, comprising: a circumferentially extending tubular body from which a pair of opposite flanges extends outwardly to define a seat for housing a tire, said tubular body including at least one annular peripheral side pocket for housing a plurality of circumferentally alligned permanent magnets, spacer means being inserted in said annular side pocket in order to keep said permanent magnets at predetermined distances from each other, said spacer means including an annular strip which is inserted inside said side pocket and to which said permanent magnets are fixed, characterised in wherein said strip has a plurality of shaped seats able to receive corresponding permanent magnets said shaped seats formed of transverse alternating folds providing an undulated profile.
 2. The rim structure according to claim 1, wherein said predetermined relative distances are substantially the same along the entire extension of said tubular body.
 3. The rim structure according to claim 1, wherein said side pocket has a quadrilateral cross-section, with an external side wall arranged in a plane substantially perpendicular to the axis of rotation of the rim.
 4. The rim structure according to claim 1, wherein said tubular body has longitudinal ends facing each other and connected by means of a pin.
 5. The rim structure according to claim 4, wherein said tubular body comprises an annularly extending main cavity inside which said pin is inserted with interference at said facing ends.
 6. The rim structure according to claim 4, wherein said tubular body comprises a secondary cavity inside which a corresponding pin is inserted with interference at said longitudinal facing ends.
 7. The rim structure according to claim 1, wherein the base material of said strip is chosen from among ferromagnetic or non-magnetic metallic materials.
 8. The rim structure according to claim 1, wherein the base material of said strip is chosen from among synthetic materials or composite materials which are suitably reinforced.
 9. The rim structure according to claim 1, wherein said spacer means comprises a plurality of non-magnetic inserts which are arranged inside said side pocket, alternating with said permanent magnets.
 10. A method for manufacturing a rim structure, comprising the steps of a) preparing a substantially straight tubular body having a length substantially equal to the circumferential extension of the rim structure; b) preparing a plurality of permanent magnets; c) preparing means for spacing said permanent magnets; d) inserting said plurality of permanent magnets and said spacers inside a side pocket of said tubular body so as to keep said permanent magnets at predetermined distances from each other; e) bending said substantially straight tubular body so as to provide it with a circular form having substantially aligned longitudinal ends; f) joining together said longitudinal ends so as to provide a continuous rim structure, wherein said step of preparation of said means for spacing said permanent magnets comprises preparing a strip of laminar material and subjecting said strip to plastic deformation to provide a plurality of seats at predetermined distances from each other and being shaped to receive said permanent magnets.
 11. The method according to claim 10, wherein said bending step e) is performed after said step d) for inserting said permanent magnets and said spacer means.
 12. The method according to claim 10, wherein said bending step e) is performed before said step d) for inserting said permanent magnets and said spacer means.
 13. The method according to claim 10, wherein said permanent magnets are fixed inside said corresponding shaped seats by means of an interference fit.
 14. The method according to claim 13, wherein said strip with said permanent magnets is inserted inside said side pocket substantially along the entire longitudinal extension of said tubular body and is cut at the longitudinal ends of the latter.
 15. A machine making a rim comprising: means for continuously feeding a strip of laminar material, means for fixing a plurality of permanent magnets onto said strip, means for inserting said strip together with said permanent magnets inside a linear tubular body of predetermined length, means for cutting said strip at a longitudinal end of said tubular body, means for bending said tubular body, and means for joining together the longitudinal ends of said tubular body so as to provide a unitary rim structure, wherein said fixing means comprise means for deforming said strip so as to provide a plurality of shaped seats at predetermined distances from each other.
 16. The machine according to claim 16, wherein said fixing means further comprises a dispenser for loading one permanent magnet inside each of said shaped seats. 